Microelectronics and microelectromechanical systems (MEMS) development has demonstrated that the miniaturization of complex instruments and devices is feasible when subsystems can be miniaturized and integrated on a common platform. This miniaturization and integration have opened various markets, such as a worldwide market in telecommunications to provide instant and direct information to the user of a hand held device. This growing MEMS industry is evolving to further integrate devices, such as photonic devices onto a common platform. The insertion of photonic devices, for example, has at least two advantages. First, miniaturized components provide for an increase in the data transfer bandwidth. Second, the insertion of photonic devices enables the development of a variety of miniature analytical instrumentation that utilize optical spectroscopy for precision sensing such as that used in biological assay and chemical applications. The miniature analytical instrument application area, also called micro total analysis systems (μ-TAS), is perceived to be a growing industry. In any integrated instrument, the intelligence and memory are aptly handled by microelectronics fabrication technology. If the instrument requires sensing or control, then MEMS technology has been shown to be successful.
Many miniaturized devices can be developed using MEMS fabrication technologies for making small structures and devices, such as electromagnetic antennas, electronic capacitors, chemical reactors, mechanical motors, optical filters, and acoustic sensors, among a vast array of possible devices. The further integration of these devices onto a common platform requires an ability to make three-dimensional interconnections among these devices or a mix of devices. The existing approaches to fabricating electrical conducting structures are confined to structures in two dimensions. In so doing, two-dimensional pattern metallization processing technology can be used, such as microelectronics lithography. However, some devices do not work as well in two dimensions, such as high frequency antennas and transformers. So, the MEMS industry circumvents these limitations imposed by the two-dimensional metallization by stacking a sequence of two-dimensional electrically conducting patterns on insulating material and electrically connecting the stacks with patterned vertical vias. This assembly is not a true three-dimensional structure. However, the repetitive two-dimensional approach works well for laying out multilevel conducting lines, but has limitations when more complex three-dimensional electrical conducting structures are to be fashioned, such as with coils, inductors, and horn antennas where curvature is used to enhance efficiency. In the cases where complex high aspect ratio microelectrical structures are to be constructed, there are processing techniques for patterning metallization in true three dimensions.
In these three-dimensional processing approaches, the designed structures may have micrometer features or lengths that are in the submillimeter scale so as to require careful handling after release. To circumvent failure as a result of handling, there are device encapsulation and packaging techniques to electrically insulate and protect these small delicate structures. However, most of the processing approaches use a conformal spray or coating approach. These approaches may risk destroying the fragile device as a result of surface tension forces during the drying phase, such as with induced stresses. If the device survives the drying phase, the device is then susceptible to damage during the instrument development phase when the structure or device must be inserted or placed onto the platform by an automated pick and place machine. The potential for damage is also present when these fragile small devices are connected, such as by wire bonding and soldering, to an adjoining electrical unit using an electrical interface.
Photostructurable glass ceramic materials are used to make internal structures having internal functional surfaces defined during a photostructuring process. An entire volume is made of photostructurable material. For example, U.S. Pat. No. 6,783,920, by Livingston et al., entitled Photosensitive Glass Variable Laser Exposure Patterning Method, issued Aug. 31, 2004; U.S. Pat. No. 6,932,933, by Helvajian et al., entitled Ultraviolet Method of Embedding Structures in Photocerams; and U.S. Pat. No. 6,952,530, by Helvajian et al., entitled Integrated Glass Ceramic Systems, issued Oct. 4, 2005 teach the processing of photostructurable materials for making structures within a photostructurable volume. U.S. Pat. No. 6,830,221, by Janson et al., entitled Integrated Glass Ceramic Spacecraft, issued Dec. 14, 2004, teaches the encapsulation of the various devices within a glass ceramic volume which consists of several separate glass housing parts. However, a problem with such encapsulation is a required number of housing components integrated as a singular housing. These patents generally teach embedding photostructurable structures within a ceramic volume where the structures and volumes are all made of the photostructurable material. The encapsulation problem is similar to plastic injection machines where the two halves of a mold are pressed together, and hot plastic is injected through an injection port and conduit runners to cavities defining a desired plastic part.
The photostructurable glass ceramics are a class of materials that may be patterned in two dimensions by masks and lithography or in three dimensions by laser direct-write processing patterning. The patterning process may entail the site selective photo exposure of the material after which the material may undergo a baking step to realize the exposure effects. With a certain bake protocol, there is the in-situ growth of a crystalline phase in the exposed regions. For a specific protocol, the crystalline material is found to be etchable in dilute hydrofluoric acid, while for another bake protocol, it is not etchable. The etchable crystalline phase can be etched in excess of 30-50 times faster than the unexposed material and thereby allows for patterned structures to have aspect ratios that can exceed 50:1.
The prior photostructurable manufacturing processes do not provide a processing approach by which delicate structures and devices can be disposed in the volume for enabling functional interconnections fashioned within a protective volume. These and other disadvantages may be solved or reduced using the invention.